From c8dbca165bb090f926996a572ea2b5b577b34b70 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Fri, 30 May 2014 11:35:54 -0600 Subject: [PATCH] vfio/iommu_type1: Avoid overflow Coverity reports use of a tained scalar used as a loop boundary. For the most part, any values passed from userspace for a DMA mapping size, IOVA, or virtual address are valid, with some alignment constraints. The size is ultimately bound by how many pages the user is able to lock, IOVA is tested by the IOMMU driver when doing a map, and the virtual address needs to pass get_user_pages. The only problem I can find is that we do expect the __u64 user values to fit within our variables, which might not happen on 32bit platforms. Add a test for this and return error on overflow. Also propagate use of the type-correct local variables throughout the function. The above also points to the 'end' variable, which can be zero if we're operating at the very top of the address space. We try to account for this, but our loop botches it. Rework the loop to use the remaining size as our loop condition rather than the IOVA vs end. Detected by Coverity: CID 714659 Signed-off-by: Alex Williamson --- drivers/vfio/vfio_iommu_type1.c | 45 +++++++++++++-------------------- 1 file changed, 18 insertions(+), 27 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 6673e7be507f..0734fbe5b651 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -524,7 +524,7 @@ unwind: static int vfio_dma_do_map(struct vfio_iommu *iommu, struct vfio_iommu_type1_dma_map *map) { - dma_addr_t end, iova; + dma_addr_t iova = map->iova; unsigned long vaddr = map->vaddr; size_t size = map->size; long npage; @@ -533,39 +533,30 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, struct vfio_dma *dma; unsigned long pfn; - end = map->iova + map->size; + /* Verify that none of our __u64 fields overflow */ + if (map->size != size || map->vaddr != vaddr || map->iova != iova) + return -EINVAL; mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1; + WARN_ON(mask & PAGE_MASK); + /* READ/WRITE from device perspective */ if (map->flags & VFIO_DMA_MAP_FLAG_WRITE) prot |= IOMMU_WRITE; if (map->flags & VFIO_DMA_MAP_FLAG_READ) prot |= IOMMU_READ; - if (!prot) - return -EINVAL; /* No READ/WRITE? */ - - if (vaddr & mask) - return -EINVAL; - if (map->iova & mask) - return -EINVAL; - if (!map->size || map->size & mask) + if (!prot || !size || (size | iova | vaddr) & mask) return -EINVAL; - WARN_ON(mask & PAGE_MASK); - - /* Don't allow IOVA wrap */ - if (end && end < map->iova) - return -EINVAL; - - /* Don't allow virtual address wrap */ - if (vaddr + map->size && vaddr + map->size < vaddr) + /* Don't allow IOVA or virtual address wrap */ + if (iova + size - 1 < iova || vaddr + size - 1 < vaddr) return -EINVAL; mutex_lock(&iommu->lock); - if (vfio_find_dma(iommu, map->iova, map->size)) { + if (vfio_find_dma(iommu, iova, size)) { mutex_unlock(&iommu->lock); return -EEXIST; } @@ -576,17 +567,17 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, return -ENOMEM; } - dma->iova = map->iova; - dma->vaddr = map->vaddr; + dma->iova = iova; + dma->vaddr = vaddr; dma->prot = prot; /* Insert zero-sized and grow as we map chunks of it */ vfio_link_dma(iommu, dma); - for (iova = map->iova; iova < end; iova += size, vaddr += size) { + while (size) { /* Pin a contiguous chunk of memory */ - npage = vfio_pin_pages(vaddr, (end - iova) >> PAGE_SHIFT, - prot, &pfn); + npage = vfio_pin_pages(vaddr + dma->size, + size >> PAGE_SHIFT, prot, &pfn); if (npage <= 0) { WARN_ON(!npage); ret = (int)npage; @@ -594,14 +585,14 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, } /* Map it! */ - ret = vfio_iommu_map(iommu, iova, pfn, npage, prot); + ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage, prot); if (ret) { vfio_unpin_pages(pfn, npage, prot, true); break; } - size = npage << PAGE_SHIFT; - dma->size += size; + size -= npage << PAGE_SHIFT; + dma->size += npage << PAGE_SHIFT; } if (ret)